On one pair of brand new speakers, I noticed tonal changes over a 3 month period.

On another pair, I found the first day made a big difference. Subsequent "run-in" had little effects.

A couple of weeks ago, I measured some new driver impedances when the drivers were cold, then run them loud for an hour then immediately measured them. I found no changes whether the drivers are "cold" or "warm".

If I have pairs, I wire them parallel out of phase then feed them with some interstation FM noise (just off channel is best) for a few days in my laundry, amking sure they have some decent peak-peak movement. I do it with compression drivers too. High efficiency drivers benefit the most as they usually receive a very mild workout in the home under normal conditions so it takes a long time for suspensions to lossen a bit, if they need it.

Costs nothing but a bit of time and electricity and it makes almost no noise.